A typical conventional portable telephone is adapted to notify the user about an incoming call by sound (ringing tone) and another type of portable telephone is designed to notify the user about an incoming call additionally by vibrating a built-in vibrator of a portable telephone body in order to prevent a nuisance from being cause to those around the user due to the generation of noise. Although this type of portable telephone is certainly able to eliminate the noise caused by the ringing tone, the disadvantage is that when the portable telephone is put into a bag or a pocket of a suit jacket that has been taken off, it is not possible to notify the user about an incoming call.
Therefore, a so-called independent vibrator type portable telephone has been proposed in that the user is notified of an incoming call by causing a small vibrator which is provided separately from the portable telephone body to vibrate when the incoming call is received. The vibration of the separated vibrator is generated by rotating a motor as a vibration source intermittently for a predetermined time when the portable telephone body detects the incoming call and instructs the vibrator to vibrate; that is, the whole vibrator is then vibrated to notify the user about the incoming call and subsequently its operation is stopped.
With the independent vibrator type portable telephone like this, the user is supposed to keep carrying the vibrator about the body so that the user may sense the vibration of the vibrator with the skin, whereby even though the portable telephone is put in a bag or placed somewhere separately from the body, the user is certainly notified of the incoming call.
The aforementioned independent vibrator type portable telephone is designed to transmit a radio wave W2 from the portable telephone to the vibrator in addition to a radio wave W1 from the portable telephone to a base station. The radio wave W2 is transmitted as a command signal from the portable telephone to the vibrator when an incoming call is received by the portable telephone from the base station, whereby the vibrator starts vibrating to notify the user about the incoming call.
While the radio wave W2 is being transmitted from the portable telephone to the vibrator, however, if the radio wave W1 is simultaneously transmitted from the portable telephone to the base station, the radio wave W1 directed to the base station may interfere with the radio wave W2 directed to the vibrator in a portion where both the radio waves are superimposed as shown in FIG. 25 because the radio wave W1 is stronger than the radio wave W2. Therefore, the command signal fails to reach the vibrator and no vibration is generated therefrom, whereupon the user is not notified of the incoming call.
In the case of such a portable telephone as mentioned above, the vibrator detects a radio wave for use in transmitting an ST (control tone) signal or a DST (digital control tone) signal to the base station through a voice channel and vibrates itself until the user sets the portable telephone off hook against an incoming call from the base station.
Since the vibrator keeps detecting the transmission wave sent out by the portable telephone in the prior art method, however, it may detect a radio wave in the neighborhood of 900 MHz sent out by anything other than the portable telephone. Therefore, the vibrator may start vibrating as it misjudges that an incoming call is received by itself though no incoming call is received by the portable telephone.
In addition to the problem above, there is another one arising from a case where the vibrator starts vibrating though no incoming call is received by the proper portable telephone because the vibrator detects the radio wave sent out by a portable telephone carried by a person other than the owner of the vibrator.
In the case of a small portable receiver such as a pager, a loop antenna as described in Postexamined Japanese Patent Publication 53-30977/(1978) is employed. FIG. 26 shows a conventional loop antenna.
As shown in FIG. 26, the surface of a grounded board 834 intersects the open face of a loop antenna 832 and as shown in FIG. 27, the open face of the loop antenna 832 is disposed in a direction perpendicular to the tangent of the side face 838 of the human body at the time the portable receiver is fitted thereto (e.g., put into a pocket). Further, a tuning capacitive capacitor 835 is juxtaposed between one end portion 832a of the loop antenna 832 and the grounded board 834. The other end portion 832b of the loop antenna 832 and the grounded board 834 are short-circuited and the loop antenna 832 is supplied with power from a tap feeding part 837.
The loop antenna 832 is hardly affected by the human body since the loop antenna 832 is arranged so that the side face 838 of the human body and the loop face are set perpendicular to each other by making most of the advantage of a magnetic-field type antenna. When the grounded board 834 is considered as a criterion, the tap feeding part 837 simultaneously has the factor of a monopole antenna which is top-loaded with the loop antenna 832 and also operates as an electromagnetic type antenna. Since magnetic-field and electromagnetic-field type polarized wave faces intersects in view of the construction of the loop antenna 832, the portable receiver is capable of dealing with both the vertical-horizontal polarized waves.
However, the loop of the loop antenna 832 has to be wound on the grounded board 834 perpendicularly and when the loop antenna 832 is adopted in the small portable receiver, the open area of the loop is hardly enlarged. Therefore, its gain deteriorates and consequently the drawback is that the malfunction of the receiver is incurred.
Since the loop is designed to be wound across the grounded board 834, parts on the grounded board 834 tend to be badly affected when they are installed close to one another and the drawback is that the malfunction of the receiver due to gain deterioration and characteristic variations at the time mass production (variations in the positional relation between each part and the loop at the time of assembly) are brought about.
An object of the present invention is to provide a communication system of a portable communication terminal, an incoming call control system of a portable communication terminal and an incoming call notifying device of a portable communication terminal capable of obviating the malfunction of a vibrator as the drawback of a conventional independent vibrator type portable terminal.